1. Field of the Invention
The present invention relates to a microchip for treating a sample.
2. Description of the Background Art
A technique referred to as Lab on Chip separating, reacting, mixing, measuring and detecting a biomaterial such as an enzyme, protein, a virus or a cell on a substrate of several mm to several cm in size has recently been watched in the fields of medical care, food, pharmaceuticals and the like. Chips employed in Lab on Chip are generally referred to as microchips, and include a clinical analysis chip, an environmental analysis chip, a gene analysis chip (DNA chip), a protein analysis chip (proteome chip), a sugar chain chip, a chromatograph chip, a cell analysis chip, a pharmaceutical screening chip and the like, for example.
A microchip is provided with treatment portions performing the aforementioned separation, reaction, mixing, measurement and detection, a retention portion retaining a reagent, an untreated sample, a waste liquid resulting from the treatments and the like and channels. The channel connects the treatment portions with each other and with the retention portion, so that a small quantity of liquid can be moved from and to the retention portion and the treatment portions. In order to control such movement of the liquid, a valve is provided in the microchip.
FIG. 16(a) shows an exemplary valve described in National Patent Publication Gazette No. 2001-503854. The valve shown in FIG. 16(a) is formed in a microchip, and includes a left reservoir 1a, a right reservoir 1b and a tube 2 connecting left and right reservoirs 1a and 1b with each other. The sectional areas of left and right reservoirs 1a and 1b are larger than that of tube 2. If the contact angle θ of a liquid is at least 90°, pressure on the interface between left reservoir 1a and tube 2 acts in a direction for keeping the liquid in left reservoir 1a. If the contact angle θ is at least 90°, therefore, the liquid in left reservoir 1a is introduced into tube 2 through application of pressure, and further introduced into right reservoir 1b through application of prescribed pressure. If the contact angle θ of the liquid is less than 90°, on the other hand, the pressure on the interface acts in a direction for drawing the liquid into tube 2 due to capillary attraction, so that the liquid in left reservoir 1a is drawn into tube 2. Then, the liquid is introduced into right reservoir 1b through application of the prescribed pressure. Thus, the reservoirs and a channel having different sectional areas are connected with each other for facilitating the function of the valve.
Japanese Patent Laying-Open No. 2003-270252 discloses a technique of sealing a liquid in a prescribed place by solidifying and charging a soluble valve and passing the liquid by contrarily dissolving the valve by heating or the like.
Further, Japanese Patent Laying-Open No. 11-257231 (1999) discloses a valve mechanically opening/closing a channel. This valve is constituted of an elastic valve diaphragm and a packing, and deformed by a piezoelectric element for opening/closing the channel.